When cancer treatment ends, people often expect relief. Instead, many feel unmoored.
The appointments slow down. The calendar opens. Friends say, “You must be so happy to be done.” And yet the body does not exhale. Sleep fragments. Anxiety spikes. Fatigue deepens. New pains appear. The sense of vigilance that once had a clear target now floats without an object.
This is not a failure of gratitude or resilience. It is biology.
Chemotherapy, radiation, surgery, immunotherapy, and even short-term targeted treatments all train the nervous system to stay alert. Threat was real. Urgency was appropriate. When treatment stops abruptly, the body is often the last to get the memo. Survivorship begins not with restoration, but with recalibration.
This post is about that first quiet, destabilizing phase. Not “back to normal,” but not actively being treated either. Just after and forever.
Art by Nathalie Latham from her book I AM ALIVE. Nathalie was diagnosed with stage 3 cervical cancer at 39. Her work is like watching a nervous system find language when words alone are not enough. Used with permission.
What is actually happening in the body
During treatment, the nervous system operates in a sustained stress response. Cortisol patterns shift. The hypothalamic-pituitary-adrenal axis stays activated. Inflammatory cytokines remain elevated. Sleep architecture changes. The gut-brain axis is disrupted by both the treatments themselves and the stress of living under threat.
When treatment stops, these systems do not simply reset. The HPA axis may remain dysregulated for months, even years. Cortisol rhythms can flatten, meaning the body loses the normal peaks and dips that regulate energy, mood, and sleep. Inflammatory markers often stay elevated well beyond the last infusion. The nervous system, in a very real sense, is still behaving as though threat is present.
I see this in my patients regularly. They come in weeks or months after finishing treatment and say some version of the same thing: “I should feel better. Why don’t I feel better?” The answer is usually that their body is still running a program that was appropriate during treatment and has not yet received the signal to stand down.
The cortisol piece
Cortisol deserves specific attention here. In a healthy system, cortisol follows a diurnal rhythm: it peaks in the morning to help you wake up and declines through the day, reaching its lowest point at night. This rhythm governs energy, focus, immune activity, blood sugar regulation, and sleep onset.
Image adapted from Karaboué et. al. British Journal of Cancer (2024).
A recent review by Karaboué and colleagues in the British Journal of Cancer (2024) includes a figure that makes this visible. In healthy subjects, plasma cortisol follows a clean arc: rising sharply in the early morning, peaking around 07:00 to 08:00, and steadily declining through the evening. Now compare that to the cortisol curves from four individual patients with advanced cancer. The patterns are flattened, erratic, or inverted. Some show almost no morning rise at all. This is what I mean when I say the rhythm is disrupted. It is measurable, and it has downstream consequences for immune function, energy, sleep, and recovery.
I check salivary cortisol patterns in many of my post-treatment patients, and what I frequently see is a blunted morning cortisol with elevated evening levels. This is a pattern consistent with HPA axis dysregulation, and it explains a great deal of the fatigue, insomnia, and anxiety that patients describe.
Addressing this is not about “lowering stress.” It is about actively restoring a rhythm that was disrupted. That looks different for each person, but it often involves circadian rhythm support through light exposure, meal timing, and sleep hygiene. It can also involve adaptogenic herbs, targeted nutrients, or even physiological dose of certain medications, such as prednisone, depending on the individual’s labs and clinical picture.
Sleep is not optional
I want to be direct about this: sleep is one of the most important things you can address in early survivorship.
Poor sleep after treatment is extremely common. It is also extremely consequential. Sleep is when the immune system does much of its repair work. It is when inflammatory cytokines are cleared. It is when the brain processes trauma. It is when growth hormone is released for tissue recovery. Without adequate sleep, every other intervention I recommend works less effectively.
Image credit: Neuroimmune Aspects of Sleep and Wakefulness.
And yet sleep disruption is often blushed under the post-treatment rug. “It will get better… eventually.” Patients are often left to figure it out on their own, or they are handed a prescription for a sleep aid that doesn’t address the root cause and doesn’t allow REM sleep. In my practice, I want to understand why sleep is disrupted before I intervene. Is it a cortisol pattern issue? Is it anxiety-driven hypervigilance? Is it melatonin depletion from treatment? Is it pain? Is it hormonal, especially in patients who experienced chemotherapy-induced menopause?
The answer determines the approach. A patient with flattened cortisol rhythm needs different support than a patient with post-treatment PTSD-driven insomnia. One size does not fit all.
The unfortunate reality of a disrupted circadian rhythm is that improvement is often gradual and measured in months. Root-cause work is slow medicine, but it is also the kind that lasts.
The gut remembers what you wish to forget
At least half of my post-treatment patients come in with GI complaints that did not exist before their diagnosis.
Chemotherapy damages fast-dividing cells, and the intestinal lining turns over every three to five days. That makes it one of the first casualties. Mucositis, the inflammation and ulceration of the GI tract, is well-documented. But even after the visible damage heals, the functional disruption often lingers. The bloating, the irregular motility, the new food intolerances. Sometimes they resolve. Often they do not.
What I commonly see: a patient who tolerated dairy and gluten just fine before treatment and now reacts to both. A patient with persistent bloating and gas who has been told their scans look clean, so there is nothing wrong. A patient on long-term acid suppression from the PPIs prescribed during chemo who now has low stomach acid, poor protein digestion, and creeping nutrient deficiencies in B12, iron, and magnesium. These are not mysterious. They are predictable consequences of what treatment does to the GI tract.
The microbiome piece matters here too. Chemotherapy and the antibiotics frequently given alongside it can significantly reduce microbial diversity. This is not a minor detail. The gut microbiome influences immune function, neurotransmitter production, estrogen metabolism, and systemic inflammation. A post-treatment microbiome that has lost key species is not just a digestive issue. It is a whole-body issue.
In my practice, I often start with a comprehensive stool test like a GI MAP or GI Effects to get a functional picture of what is happening: bacterial balance, inflammatory markers like calprotectin and secretory IgA, pancreatic enzyme output, and whether there are overgrowths that need to be addressed. From there, the approach depends on what the test shows. For a patient with evidence of intestinal permeability, I might use L-glutamine and zinc carnosine to support mucosal repair. For someone with post-antibiotic dysbiosis, specific probiotic strains like Saccharomyces boulardii or Lactobacillus rhamnosus GG can help, but a broad-spectrum “probiotic blend” off the shelf is not always the right move. For a patient who developed SIBO during or after treatment, I need to address that directly before layering on probiotics that could make it worse. If you are suspecting SIBO Dr. Angela Lucterhand breaks down the complexities of diagnosing and treating SIBO in a way that is both thorough and accessible here.
The emotional landscape
I believe this part of survivorship is profoundly underserved.
Patients are expected to feel grateful when treatment ends. And many do feel grateful, alongside a tangle of other emotions that do not fit neatly into that narrative: fear of recurrence, grief for what was lost during treatment, identity disruption, relationship strain, anger, guilt for not feeling happy enough, and a strange loneliness that comes from no longer being actively cared for by a medical team.
Art by Nathalie Latham, from her book I AM ALIVE. I do not feel safe although they say I am out of danger
although they say I am out of danger
although they say I am out of danger
This is not a psychological weakness. It is a normal response to an abnormal experience. The body and mind went through something significant, and the transition out of active treatment can feel like stepping off a moving train.
I do not separate emotional care from physical care. In my experience, correcting cortisol dysregulation often eases anxiety. Restoring sleep reduces emotional reactivity. Supporting the gut-brain axis can meaningfully shift mood. Even patients who are initially reluctant frequently benefit from psychotherapy and peer support.
I spent many years working with end-of-life and terminally ill patients using psychedelic-assisted therapy. In the right setting, with proper screening and clinical support, I have witnessed patients process years of accumulated fear and grief in a single session. This is not fringe science. There is a growing body of research on psilocybin-assisted therapy for cancer-related existential distress, and the results are significant. It is not appropriate for everyone, but for the right patient, it can be a turning point that talk therapy alone does not reach.
Where to start: the first 90 days
If you have recently finished cancer treatment and feel like your body has not caught up to the good news, here is where I typically begin with patients:
Assess what treatment left behind. This means comprehensive lab work beyond what your oncology team may routinely order. I look at a four- or five-point salivary cortisol to map the daily rhythm, not just a single morning draw. Thyroid function including free T3 and reverse T3, because chemotherapy can quietly shift conversion. Sex hormones, especially in patients who went through chemo-induced menopause or are now on endocrine therapy. Metabolic markers like fasting insulin and HbA1c, because insulin resistance frequently develops during treatment and can show up on labs long before HbA1c shifts. Inflammatory markers like hsCRP, IL-6, and ferritin. Nutrient levels including RBC magnesium, B vitamins, vitamin D, and zinc. Immune markers including Neutrophil-to-Lymphocyte Ratio, or NLR (optimal between 1.0 and 2.0, indicating low systemic inflammation and balanced immunity), lymphocyte subsets, and natural killer cell function (optimal above 20 LU). You do not need fancy out-of-pocket labs. Most of these are available through your local laboratory.
Prioritize sleep, but investigate first. I do not hand someone melatonin or trazodone and call it a day. If a patient is waking at 2 or 3 AM every night, I want to know if cortisol is spiking at that hour, if blood sugar is dropping, or if it is anxiety-driven hypervigilance. For a patient with a flattened cortisol curve, I might use phosphatidylserine in the evening to help lower nighttime cortisol. For someone whose melatonin production was disrupted by treatment, I will often start with a low dose of melatonin, typically 1 to 3 mg, timed correctly. For anxiety-driven insomnia, the intervention might be magnesium glycinate, L-theanine, or a referral for CBT-I. The point is: the “why” determines the “what.”
Support the nervous system directly. I tell my patients that the nervous system responds to predictability and safety signals. Practically, that means consistent wake times, morning sunlight within the first 30 minutes of the day, meals at regular intervals, and movement that is not punishing. I am a fan of vagal toning exercises like slow-paced breathing, specifically exhale-dominant patterns at about five to six breaths per minute. Brad S Lichtenstein ND BCB is my go-to resource for all things biofeedback and his work is a good place to start if you want to understand how training your nervous system actually works. Humming, gargling, and cold water face immersion also activate the vagus nerve. These are simple, free, and effective. For patients who feel completely wired, I sometimes start with supplements such as 200mg Zen, REM Maintenance, or Cortisol Manager, dosed based on where they are in their cortisol pattern.
Address nutrient depletion with intention. Platinum-based chemotherapy depletes magnesium. Methotrexate depletes folate. Prolonged treatment with proton pump inhibitors during chemo often tanks B12 and iron absorption. I see post-treatment vitamin D levels in the teens regularly, even in patients who were supplementing 2000IU/day. I test before I supplement, and I dose based on labs, not guesswork. For example, a patient with a vitamin D level of 18 ng/mL would get 10,000IU/day of Vitamin D (plus K2), vs for someone at 48 ng/mL (w/o supplementation) 5,000IU/day of Vitamin D may be enough. I also check RBC magnesium rather than serum, because serum magnesium can look normal while intracellular stores are depleted.
Do not rush back to “normal.” I had a patient who told me she felt guilty for still napping at 2 PM, three months out from her last cycle. She thought something was wrong with her. Nothing was wrong. Her body was still rebuilding, and the nap was doing more for her recovery than the pressure to power through it. The pressure to resume pre-cancer life immediately is real and often self-imposed. I tell patients to think of the first 90 days as a rebuilding phase. Increase activity by about 10 percent per week. Let your energy and your intuition guide the pace, not your calendar or anyone else's expectations.
If you are in this new unknown space and looking to connect with other, here are some brave voices on Substacks about life with and after cancer:
The hard part was supposed to be over. It is okay that it is not.
This is Part 1 of a three-part series on life after cancer treatment. Part 2 covers living under the shadow of ongoing therapy: aromatase inhibitors, tamoxifen, ADT, and long-term maintenance regimens. Part 3 addresses the long tail of uncertainty that comes with modern immunotherapy and targeted treatments.
Educational content only. This is not medical advice and does not replace individualized care with your oncology team.
For one-on-one consultations, visit drkseniamalarkey.com.
Art by Nathalie Latham, from her book “I am Alive”
Wow, thank you for writing this. I felt like someone was hugging me and saying - everything you are feeling is valid and real, here are the facts behind it. Thank you so much for the call out as well, grateful for this community of people who can support each other in the awfulness that is cancer. xx
I wish I could ban all use of “back to normal” with cancer patients.